What are convection currents and what causes them?

Convection currents are caused when there is uneven heating of the fluid. They occur in liquids and gases.
The warm air rises and the cool air flows in under it to replace it. This causes a cycle, as more air heats and rises and more cooler air flows in to replace it.

Convection is the flow of heat through a bulk, macroscopic movement of matter from a hot region to a cool region, as opposed to the microscopic transfer of heat between atoms involved with conduction. Suppose we consider heating up a local region of air. As this air heats, the molecules spread out, causing this region to become less dense than the surrounding, unheated air. For reasons discussed in the previous section, being less dense than the surrounding cooler air, the hot air will subsequently rise due to buoyant forces – this movement of hot air into a cooler region is then said to transfer heat by convection.
Heating a pot of water on a stove is a good example of the transfer of heat by convection. When the stove is first turned on heat is transferred first by conduction between the element through the bottom of the pot to the water. However, eventually the water starts bubbling – these bubbles are actually local regions of hot water rising to the surface, thereby transferring heat from the hot water at the bottom to the cooler water at the top by convection. At the same time, the cooler, more dense water at the top will sink to the bottom, where it is subsequently heated.

What Causes Convection Currents

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What are convection currents and what causes them?


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Magma is molten rock: Any differences in density, but particularly density differences due to differences in temperature, will cause the denser (cooler) liquid to sink, and hotter, lighter material to rise – this is convection. So if there is a heat source at depth within a magma chamber, (Like the presence of hotter basaltic magma in an andesitic magma – see last ref) this will set up a convection current within the magma chamber with hot magma rising, and cooling as it does so, until it becomes cool enought to sink again. This convection is limited to the magma chamber, and therefore does not drive plate tectonics except insofar as it drives the extrusion and intrusion of basaltic magma at the mid-ocean ridges. It is also possible to change the density of the magma by crystallising and settling out the heavier components (magma differentiation) – However, this would not be true convection which involves the transfer of heat. You often read about convection of the mantle (see ref. below) – this convection takes place in the solid state – the rocks are solid but plastic, and hence able to flow – this is not a magma, though. It is this Mantle convection that drives plate tectonics – there seems to be some confusion about the differences between the two.

WHAT are convection currents?i know what convection is but convection currents?

convection currents are when hot air rises pushing the cold air down so that it in turn heats and rise again causing a cycle

Can someone else tell me an easier answer?

Convection is just a fancy term for motion within a medium (water, air, magma, etc.).

A common use of the term convection relates the movement of heat. In this case, the heat itself often causes motion in the fluid motion, while also being transported by it.

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